Vaquitas are the smallest and most endangered species of the cetacean order and are found only in the northern end of the Gulf of California. The vaquita is stocky and has a classic porpoise shape. The species is distinguishable by the dark rings surrounding their eyes, patches on their lips, and a line that extends from their dorsal fins to their mouth. Their back is a dark grey that fades to a white underside. As vaquitas mature, the shades of grey lighten. [7] Female vaquitas tend to grow to be a bit larger than the male. Females usually end up at a length of 140.6 cm, compared to the males 134.9 cm. The lifespan, pattern of growth, seasonal reproduction, and testis size of the vaquita are all similar to that of the harbour porpoise.[8] The flippers are proportionately larger than other porpoises' and the fin is taller and more falcate. The skull is smaller and the rostrum is shorter and broader than in other members of the genus. The females are discernible from the males due to their larger size.[7]

Vaquitas use high-pitched sounds to communicate with one another and for echolocation to navigate through their habitats. They generally seem to feed and swim at a leisurely pace. Vaquitas avoid all boats and are very evasive. They rise to breathe with a slow forward motion and then disappear quickly. This lack of activity at the surface makes them difficult to observe.[9] Vaquitas are usually alone unless they are accompanied by a calf,[10] meaning that they are less social than other dolphin species. They may also be more competitive during mating season.[11] They are the only species belonging to the porpoise family that live in warm waters.[12] Vaquitas are nonselective predators.[13]

Like other Phocoena, the vaquita are usually seen by themselves. If they are seen together, it is usually in small groups of 2 to 3 individuals.[7] Less often, groups of around 8 to 10 have been observed, with the most ever seen at once being 40 individuals.

Vaquitas tend to forage near lagoons.[7] All of the 17 fish species found in vaquita stomachs can be classified as demersal and or benthic species inhabiting relatively shallow water in the upper Gulf of California. Vaquitas appear to be rather nonselective feeders on small fish and squid in this area. Some of the most common prey are teleosts (fish with bony skeletons) such as grunts, croakers, and sea trout.[14] Like other cetaceans, vaquitas may use echolocation to locate prey. It also is possible they locate their prey by following the sounds of prey movement.[1]

Little is known about the life cycle of vaquitas. Researchers are still determining things such as their age at sexual maturity, longevity, reproductive cycle and population dynamics. Estimates have been made but further research is needed to establish these values. Most of these estimates come from vaquitas that have been stranded or caught in nets. Some are based on other porpoise species similar to vaquitas.

It is believed that vaquitas live approximately 20 years in ideal conditions.[15][16] Vaquitas sexually mature at 1.3 meters, as early as 3 years but more likely at 6 years old. Reproduction occurs during late spring or early summer. Their gestation period is between 10 and 11 months. They have seasonal reproduction, and usually have one calf in March. The interbirth period, or elapsed time between offspring birth, is between 1 and 2 years. The young are then nursed for about 6 to 8 months until they are capable of fending for themselves.[17]

The habitat of the vaquita is restricted to the northern area of the Gulf of California, or Sea of Cortez.[4] Vaquitas live in shallow, murky lagoons along the shoreline. They rarely swim deeper than 30 meters and are known to survive in lagoons so shallow that their back protrudes above the surface. The vaquita is most often sighted in water 11 to 50 metres deep, 11 to 25 kilometres from the coast, over silt and clay bottoms. Vaquitas tend to choose habitats with turbid waters, due to the fact that they have high nutrient content.[1] The high nutrient content is important because it attracts the small fish, squid, and crustaceans that they feed on. They are able to withstand the significant temperature fluctuations characteristic of shallow, turbid waters and lagoons.

A vaquita swims in the foreground while fishing boats ply their trade in the distance.

Vaquita have never been hunted directly, but it is known that the vaquita population is declining. The decline is largely due to animals becoming trapped in gillnets intended for capturing the totoaba, another species endemic to the Gulf. Estimates placed the vaquita population at 567 in 1997.[4] With their population dropping as low as 150 individuals in 2007 and possibly even lower today, inbreeding depression may have begun to affect the fitness of the species, potentially contributing to the population’s further decline.[18]

Studies performed in El Golfo de Santa Clara, one of the three major ports in which vaquitas live, indicated that gillnet fishing causes approximately 39 vaquita deaths a year. This is close to 17% of the whole vaquita population within this port. While these results were not taken from the entire range of habitat in which vaquitas live, it is reasonable to assume that these results can be applied to the whole vaquita population, and in fact may even be a little low.[20] Even with a gillnet ban throughout the vaquita refuge area, which contains 50% of the vaquita’s habitat, the population is still in decline, which suggests a complete ban of gillnet use may be the only solution to saving the vaquita population.[21]

Other potential threats to the vaquita population include habitat alterations and pollutants. The habitat of the vaquita is small and the food supply in marine environments is affected by water quality and nutrient levels. The damming of the upper Colorado river has reduced the inflow of freshwater into the gulf, potentially affecting the vaquita.[15] In addition, the use of chlorinated pesticides may also have a detrimental effect. Despite these possible problems, it is important to note that most of the recovered bodies of the vaquitas show no signs of emaciation or environmental stressors,[15] implying that the decline in the vaquita population is due almost solely to bycatch. However these additional hazards may pose a long term threat.

Though the major cause of vaquita porpoise mortality is bycatch in gillnets, as numbers continue to dwindle new problems will arise that will tend to make recovery more difficult. One such problem is reduced breeding rates. With fewer individuals in the habitat, there will be less contact between the different sexes and consequently less reproduction. This may be followed by increased inbreeding and reduced genetic variability in the gene pool, following the bottleneck effect.

When inbreeding depression occurs, the population experiences reduced fitness because deleteriousrecessive genes can manifest in the population. In small populations where genetic variability is low, individuals are more genetically similar. When the genomes of mating pairs are more similar, recessive traits appear more often in offspring. The more related two individuals are in the breeding pair, the more deleterious homozygous genes the offspring will likely have which can greatly lower fitness in the offspring.[22] It is important to note that these secondary impacts of dwindling vaquita numbers are not necessarily a threat yet, but they will become problematic if the vaquita population continues to decline.[23]

Removal of the vaquita will have a significant ecological impact on the northern Gulf of California. The Gulf of California is considered a large marine ecosystem, due to its high species diversity and large habitat size.[24] With such biodiversity in the region, it is important to consider the potentially harmful effects of drops in the vaquita population on seemingly unrelated species due to apparent competition.

Sharks have been determined to be the only predators of vaquitas. Due to its limited number of predator species, the vaquita population is sensitive to small changes in predation from sharks.[24] Although the vaquita accounts for only a small percentage of the diets of sharks in the region, extinction of the vaquita could potentially cause negative effects on shark population sizes. Extinction of the vaquita may also impact the vaquita prey populations in the northern Gulf ecosystem. The disappearance of the vaquita could lead to potential over-population of their prey species such as benthic fishes, squid, and crustaceans.[15]

Conservation efforts for the vaquita are mainly focused on fishing restrictions to prevent vaquita bycatch. These fishing restrictions could prove beneficial for the fish in the upper gulf as well as the vaquita. As a result of increased restrictions on gillnet use, the populations of the targeted fish and shrimp species will receive protection from overfishing.[25] Historically, numerous commercially fished species have experienced devastating impacts due to overfishing, and the vaquita conservation program may lessen the severity of such devastation in the future.[25] Another solution to prevent vaquita bycatch might be to redesigning fishing nets. A redesigned net could be used to effectively catch fish but leave the vaquita untouched.

Because vaquitas are indigenous to the Gulf of California, Mexico is predominantly leading conservation efforts with the creation of the International Committee for the Recovery of the Vaquita (CIRVA), which has attempted to help prevent the accidental deaths of vaquita by outlawing the use of fishing nets within the vaquita’s habitat.[7] CIRVA has worked together with the CITES, the ESA, and the Marine Mammal Protection Act (MMPA) to make a plan to nurse the vaquita population back to a point at which they can sustain themselves.[9] CIRVA concluded in 2000 that between 39 and 84 individuals are killed each year by such gillnets. In order to try to prevent extinction, the Mexican government has created a nature reserve covering the upper part of the Gulf of California and the Colorado River delta. CIRVA recommends that this reserve be extended southwards to cover the full known area of the vaquita's range and that trawlers be completely banned from the reserve area.

On October 28, 2008, Canada, Mexico, and the United States launched the North American Conservation Action Plan (NACAP) for the vaquita, under the jurisdiction of the Commission for Environmental Cooperation (CEC), a NAFTA environmental organization.[26] The NACAP is a strategy to support Mexico’s efforts to recover the vaquita. Also in 2008 Mexico launched the program PACE-VAQUITA, another effort to help preserve the species. PACE-VAQUITA compensates fishermen who choose one of three alternatives: rent-out, switch-out, and buy-out.

In the rent-out option fishermen acquire temporary contractual obligations to carry out conservation efforts. They are paid if they agree to terminated their fishing inside the vaquita refuge area.There is a penalty if fisherman breach the contract which includes getting their vessels taken by the government. The switch-out option provides fishermen with compensation for switching to vaquita-safe harvesting technology. Finally the buy-back program compensates fisherman for permanently turning in their fishing permits as well as their respective gear.[27] In 2008, because of how few fisherman were enrolling in the switch-out option, PACE Vaquita added a yearly, short-term option for fisherman. The fisherman could simply rent the vaquita safe fishing equipment yearly for compensation. Then, in 2010, this option was broken down even further. Fisherman now had the option of buying the vaquita-safe net, or they could do the yearly rent, but for less compensation.[16] Despite these efforts the probability that these attempts at conservation will work is slim. Only about a third of fishermen in the area have accepted to these terms so far. Some fishermen continue to fish in the protected areas despite the economic alternatives. Even measuring the population size of the vaquita will be difficult as the rarity of the vaquita bycatch will make it difficult to demonstrate the difference these programs are creating.[27]